Prozoach- Believe it or not I find the navy chambray which is the darkest to be quite soft and airy; similar to madras for some reason.
Friday Frenzy- the Warzones are indeed very thick would not recommend for summer; the royals are also in my opinion to 'shiny' for casual shirting. I would go with ecru if I were going for an Oxford or I'd go with an even more summery fabric such as linen cotton or even Chambray as Joiji recommended.